Sigma C 23 mm f/1.4 DC DN review - Coma, astigmatism and bokeh

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Sigma C 23 mm f/1.4 DC DN

17 June 2024

Maciej Latałło

7. Coma, astigmatism and bokeh

It is very difficult to correct coma in a fast, wide angle lens, that's why we are not surprised the tested Sigma had some problems in this area. Coma makes itself felt but it is a bit comforting that on stopping down the aperture by one full EV stop you can reduce it noticeably.

In this category the Sigma finds itself once again in the middle of the group but the order is reverted: the Fujinon corrects coma the best, the Viltrox is the weakest.

X-T2, f/1.4, center	X-T2, f/1.4, Corner

X-T2, f/2.0, center	X-T2, f/2.0, Corner

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Astigmatism, understood as an average difference between horizontal and vertical MTF50 function values, amounted to 4.4%, a value on the borderline between very low and low levels, far better than the results of the rivals. What's more, this aberration is noticeable only by f/1.4 because up from f/2.0 it becomes completely negligible.

When it comes to light spread, defocused circles of light look good, without any heterogeneity or local extreme points. Using two aspherical elements causes a delicate onion ring bokeh structure. Mechanical vignetting also makes itself felt a bit, as it remains visible without any problems by f/1.4 and f/2.0. Overall, for a wide angle lens, out-of-focus images produced by the Sigma look good and in this category we don't have any serious reservations.